1 files changed, 35 insertions, 0 deletions
diff --git a/sql/cset_narrowing.cc b/sql/cset_narrowing.cc
new file mode 100644
index 00000000..abdaec16
--- /dev/null
+++ b/sql/cset_narrowing.cc
@@ -0,0 +1,35 @@
+/*
+   Copyright (c) 2023, MariaDB Corporation.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; version 2 of the License.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1335  USA */
+
+#ifdef USE_PRAGMA_IMPLEMENTATION
+#pragma implementation				// gcc: Class implementation
+#endif
+
+#include "mariadb.h"
+#include "sql_priv.h"
+#include "sql_select.h"
+
+Charset_utf8narrow utf8mb3_from_mb4;
+
+bool Utf8_narrow::should_do_narrowing(const THD *thd,
+                                      CHARSET_INFO *field_cset,
+                                      CHARSET_INFO *value_cset)
+{
+  return optimizer_flag(thd, OPTIMIZER_SWITCH_CSET_NARROWING) &&
+           field_cset == &my_charset_utf8mb3_general_ci &&
+           value_cset == &my_charset_utf8mb4_general_ci;
+}
+